In a contemporary optical network system, a number of optical network nodes may be coupled to each other via optical fibers. Optical signals are transmitted across the optical fibers from one optical network node to another. When an optical network node is installed into an optical network system, the optical network node may have to be pre-configured. For instance, the optical fibers have to be connected to their corresponding input and output ports of the optical network node so that the optical network node can function properly.
In a contemporary optical network node, Dense Wavelength Division Multiplexing (DWDM) is performed on an incoming optical signal to divide the incoming optical signal into a number of optical signals, each carried in a different wavelength. To detect signal loss in a particular wavelength, some existing optical network nodes include an Optical Channel Monitor (OCM) to detect the optical signals on a per wavelength basis. However, the OCM is typically rather slow.
Alternatively, some of the existing optical network nodes include a feedback loop coupled between a tap and a variable optical attenuator (VOA). The tap receives optical signals from the VOA and diverts part of the optical signals to the feedback loop. In response to the signal from the tap, the feedback loop detects the signal loss in the optical signals entering the tap and causes the VOA to adjust for any optical signal loss accordingly. However, this scheme compromises the speed of signal loss detection for accuracy in the feedback loop.